Molecular and morphological identification of mealybug species (Hemiptera: Pseudococcidae) in Brazilian vineyards

Abstract

Mealybugs (Hemiptera: Pseudococcidae) are pests constraining the international trade of Brazilian table grapes. They damage grapes by transmitting viruses and toxins, causing defoliation, chlorosis, and vigor losses and favoring the development of sooty mold. Difficulties in mealybug identification remain an obstacle to the adequate management of these pests. In this study, our primary aim was to identify the principal mealybug species infesting the major table grape-producing regions in Brazil, by morphological and molecular characterization. Our secondary aim was to develop a rapid identification kit based on species-specific Polymerase Chain Reactions, to facilitate the routine identification of the most common pest species. We surveyed 40 sites infested with mealybugs and identified 17 species: Dysmicoccus brevipes (Cockerell), Dysmicoccus sylvarum Williams and Granara de Willink, Dysmicoccus texensis (Tinsley), Ferrisia cristinae Kaydan and Gullan, Ferrisia meridionalis Williams, Ferrisia terani Williams and Granara de Willink, Phenacoccus baccharidis Williams, Phenacoccus parvus Morrison, Phenacoccus solenopsis Tinsley, Planococcus citri (Risso), Pseudococcus viburni (Signoret), Pseudococcus cryptus Hempel, four taxa closely related each of to Pseudococcus viburni, Pseudococcus sociabilis Hambleton, Pseudococcus maritimus (Ehrhorn) and Pseudococcus meridionalis Prado, and one specimen from the genus Pseudococcus Westwood. The PCR method developed effectively identified five mealybug species of economic interest on grape in Brazil: D. brevipes, Pl. citri, Ps. viburni, Ph. solenopsis and Planococcus ficus (Signoret). Nevertheless, it is not possible to assure that this procedure is reliable for taxa that have not been sampled already and might be very closely related to the target species.

Figure 1. Neighbor-joining tree calculated from the number of differences between 28S haplotypes.

Bootstrap values (1,000 replications) are displayed. The 28S alignment used to compute the tree (Figure S1 in File S1) differs from the alignment of raw sequences, because regions including numerous insertions/ deletions were removed to achieve a satisfactory alignment. The 16S, ITS2, C1 and LCO haplotypes of specimens displaying each of the 28S haplotypes are given after the 28S haplotype code.

Figure 2. Distribution of mealybug species in vineyards in the Paraná, Pernambuco and Rio Grande do Sul states (Brazil).

Figure 3. Electrophoresis profile obtained with the Qiaxcel Advanced System for each PCR product from the identification kit.

Each lane corresponds to one sample, and each band to a DNA fragment. The first and last lanes contain a molecular weight ladder extending from 50